Automatic trepans



Oct. 10, 1950 M. HAINAULT 2,525,669

AUTOMATIC TREPANS Filed Dec. 1, 1947 Patented Oct. 10, 1950 UNITED STATES PATENT OFFICE AUTOMATIC TREPAN S Marcel Hainault, Paris, France Application December 1, 1947, Serial No. 789,031 In France July 25, 1947 3 claims.` (o1. 12e- 310) This invention is concerned with improvements in automatic trepans for use in perforatingthe brain-pan and which comprise an automatic stop which prevents the cutter from suddenly piercing the skull.

Trepans known heretofore comprise on one hand a cutter which performs the perforating operation and a claw or like clutch adapted, as the cutter is pressed against the skull, to throw the cutter into gear and to impart the rotational movement of a motor to said cutter, the latter being thrown out of gear automatically at the end of the perforating operation as the apex of the cutter is deprived of its rest, and on the other hand a stop consisting of a point which takes its rest on the outside of the skull adjacent to the hole drilled by the cutter, said stop being raised in proportion as the cutter sinks bythe action of a telescopic device whose rotary portion derives its movement from the rotational movement of the cutter through the medium of a gear set and a claw or like clutch by which the said rotary portion of the telescopic device is only geared with the driving portion of said clutch when the tip of the stop member finds a rest on the outside of the skull.

Thus, at the completion of the perforating operation, the cutter is disengaged automatically from the motorl and comes to a standstill while the tip of the stop member which is still in engagement with the outside of the skull prevents the cutter from getting deeper into the skull.

` However, in this known arrangement, the claw or like clutches suffer from the inconveniences that the cutter is abruptly thrown into or out of engagement with or from the rotary portion of the stop telescopic device, with the result that vibration of the cutter takes place. Such vibration is made still worse by the small play that exists between the teeth of the gear set that transmits the rotational movement of the cutter to the driving portion of the clutch which enables to gear in the rotary portion of the stop telescopic device.

For the purpose of doing away with such vibration one object of this invention is to equip the cutter and/or the rotary portion of the stop telescopic device with friction gearings.

A further object of the invention is to provide the trepan with a stop constituted by the lower `end of a sleeve in which the cutter and the rotary According to a further feature of the invention the driving-portion of the telescopic device clutch is coaxial with and driven directly by the cutter instead of being driven through a gear set as in the aforementioned known arrangement, and the stop-raising telescopic device is composed of a pair of parts coaxial with the cutter.

A further feature of the invention resides in the provision in the sleeveand more particularly in that end of the same which performs the function of a stop of notches enabling to see the end and more particularly the apex of the cutter, the lower end of the sleeve thus engaging the outside of the skull at two or more places of its periphery rather than all around the cutter.

Due to the stop engaging the skull at several places around the cutter the latter can be set in position much more easily than where one single rest is provided.

A preferred embodiment of the subject-matter of the invention will now be described by way of example, reference being had to the appended `drawing in which:

Figure l is a vertical sectional view of the trepan according to the invention with the cutter tip engaging the skull and ready to begin the Figure 3 is a sectional view taken on lineV III-III in Fig. 1.

A rotary axial member I is rotated at its upper end by known means, for instance a motor and a flexible shaft which may be rigidly coupled with member I by means of a chuck or a strap.

The member I has a tapered lower end Ila on which a bore 21 provided in the upper portion of the cutter 4 is adapted to t with its tapered surface I'Ib. The pair of surfaces Ila, Ilb provide a friction clutch. A conical sleeve made of graphite may be interposed between the surfaces of the pair.

The upper portion of the cutter 4 is slidably received in the tubular part 2 between an upper end portion in which the cutter 4 is o-peratively connected with the rotary member I through the friction clutch Ila., IIb and a lower end .position in which the surfaces Ila, Ilb are disengaged from each other. A spring 8 urges the said surfaces away from each other; said spring is housed in the bore 2'I and is pressed between the lower `end face `of part I and the bottom of the bore 2l,

3 that is, the cutter 4 itself. The cutter 4 is coupled with the rotary part l whenever the point I4 of the cutter li is laid upon such a bearing point at the outside of a skull and the spring 8 is compressed.

The cutter 4 is rotationally connected with the tubular part 2 by a key I2 slidably received in a longitudinal slot i3 in the tubular member 2. Said key i2 moves up and down in said slot I3 as the cutter i is reciprocated between its top and its bottom end position in the tubular part 2.

The downward motion of the cutter i in part 2 is limited by a shoulder 23 in part 2.

In the coupled condition of the rotary member I and the cutter i the former and the tubular part 2 partake of the same rotary motion. When the rotary member I and the cutter il are loose from each other the former revolves freely within the tubular member 2.

Secured by means of a screw 2Q on 'the outside of the tubular member 2 is a collar E@ formed with a taper skirt portion Isa.

Surrounding the lower end of the tubular member 2 are an additional tubular member 3 and a sleeve 5 whose lower end 2t acts as a stop.

The tubular member is formed with an internal taper surface ist adapted to it on the taper surface Ia. rl'he pai-r of taper surfaces Ia, EEZ) provide a friction clutch.

The lower` portion of the part 3 is provided with an outer thread i9 by means of which said part can be screwed in the sleeve 5.

An annular space 2li is left free between the tubular parts 2 and 3 which are centered with respect to each other by means of an inwardly 1 projecting ring portion formed in part 3 and in which part 2 is slidably fitted.

A spring housed in the annular space 2t urges the surfaces ido, ith o the friction clutch away from each other. With this end in view 4said spring G rests with one end thereof on the lower end race of the collar 25 and with its other end through the medium of a ring 2t and balls Sli on the ring portion in part .'5. The advantage with said ring and balls Si@ that transmit the thrust from spring s to the annular projection on part 3 isthat the rotational movement of part 28 can-not `be transmitted to part T through the spring itself in the disengaged condition of the The longitudinal displacement of part 3 with respect to part 2 is limited by a ring V3| acting `as a stop for the annular projection 25 through the medium of balls 32 interposed between said ring 3l and saidprojection 25. The purpose of said balls 32 is to prevent the rotational movement ofpart 2 and ring 3i from being transmitted irictionally to part-3.

The part 3 and the sleeve 5 provide a tele scopic device. The part t is able to rotate while the sleeve 5 is retained against rotation by a screw vil whose head is slidably received in a slot Iii in said sleeve 5, saidscrew being inserted in a non-rotary ring to which is screwed on a -further ring lli which in turn-is screwed on a nonrotary member -I I which is or can be made rigid with a handle.

rIhe rings lli) and il are provided with anges 43, i4 that straddle a flange 145 on part 2; in this manner said memberii! is retained against longitudinal displacement VVVwith respect to part I I and to the rotary part i.

The upper portion 32 of the outer surface of 'part 3 is knurled and apertures 33eme cut ingthe Wall of the sleeve 5. By acting on the knurled portion through said apertures 33 the part 3 can be rotated with respect to the sleeve 5 and thereby screwed on said sleeve 5 owing to the provision of the thread is; it is thus possible to adjust the position of the part 3 with respect to the sleeve 5.

A block it is cut in the sleeve 5 and is resiliently pressed against the part 3 by a spring leaf il secured on the sleeve 5 by means oi a screw Gil. Said block lf3 is formed with a portion iii of the thread l@ and is adapted to sprag the rotation of the part 3. The advantage with such spragging action is that the part 3 is stopped immediately as soon as the surfaces ila, I'lb or ISU., Iib are disengaged from each other.

Notches [iii are cut in the lower portion of the sleeve 5. They enable an observer to ascertain the place on the skull at which the point Iii is applied.

The operation is as follows:

First of all the position of part 3 with respect to the sleeve 5 is so `adjusted that the point is ush with the stop 2@ in the expanded condition of the spring S. Thereafter the point i4 is applied on the desired place on the skull 5-3; the spring is stressed, the cutter 4 is coupled with the rotar-y member i by means of theY friction clutch I'I'd, VIZ); the cutter is thus driven into rotation.

As point ii of the cutter i sinks int-o the skull 5B, the point 2B cornes into Contact in its turn lwith the skull 553. By pushing upwardly the ele ment 3 ascends and the element 3 screwed on the threads i@ brings about the contact of the portions -ih and 58a of the clutch with compression of the spring 5. The element 23 being always in rotation it results that the element 3 rotates in turn. Since said part is screwed Vat the threadl I in the fixed sleeve E the rotary motion imparted thereto causes said sleeve 5 to move upwards. Said ascending motion cannot exceed the downward motion of the cutter "i since otherwise the stop 5i@ would come outoi engagement with the skull and the part 3, would be disconnected from tube 2 due to the action of spring t which urges the surfaces of the friction clutch lila, I8?) away from each other.

As soon as at the completion of the perforating operation no resistance is opposed any longer to the penetration of the cutter tip the spring 8 is released and only part I goes on rotating. The stop 2t remains in engagement with the outside of the skull, so that the tip Ill of the cutter will not sink farther into the skull while rotating.

Consequently, at the completion of the perforating operation, the cutter urged downward by the spring 3 is limited in its travel by the stop 2S, its longitudinal displacement being attended with no rotary motion, so that the cutter tip is will slightly loosen the cartilages and the mem,- brane 5i from the skull -55 withoutperforating them.

It is to be understood that the above-described improvements in automatic trepans are applicable yto all perforating apparatus in which a cutter, a drill or a bit is usedl in combination with an automatic stop constituted by the lower end of a sleeve having said cutter, drill orbit arranged inside thereof as well as to all perforating apparatus in which a rotary cutter, drill or bit is used in combination with a telescopic automatic stop in the formof a sleeve or the like (and particularly,Y inthe known form of a point in non-coaxial relationito the cutter) .characterized thereby that said members are driven through frctional devices.

lower portion provides a stop adapted to rest on the skull round the hole drilled `by the cutter,`

having acylindric innerwall, being coaxial with the cutter and provided with a thread, a rst tubular member rotationally rigid with said cutter and in which the upper portion of said cutter is slidably received, an axial rotary inember whose lower portion is located within said rst tubular member, a rst friction clutch adapted to transmit the rotationa1 movement of said axial rotary member to said cutter, a spring urging the friction surfaces of the first clutch away from each other whenever the tip of said cutter nds no rest, a collar rotationally rigid with said first tubular member, a second tubular member coaxial with said cutter provided with a thread on its outer wall, said second tubular member being adapted to screw itself in said sleeve, a, second friction clutch adapted to transmit the rotationall motion of said collar to said second tubular member, an annular projection on the inner wall of said second tubular member, the inner edge of said annular projection coming into engagement with the outer wall of said first tubular member, arng above said annular projection, halls between said annular projection and said ring, a spring compressed between said collar and said ring tending to throw said second clutch out of engagement, a ring screwed on the lower end of said first tubular member and balls between said ring and'said annular projection.

2. An automatic trepan with a telescopic stop as claimed in claim 1 wherein the sleeve is progvided with notches through which said second tubular member can be rotated manually,7 for the REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,701,423 Sauveur Feb. 5, 1929 FOREIGN PATENTS Number Country Date France Apr. 24, 1910 

